Rail vehicles have progressed from the simplest vehicle having a generally fixed axle at each end and four wheels to multiple axle vehicles with rotatably attached trucks. As the requirements to carry increased loads have increased, it has been required to increase the number of weight bearing wheel and axle assemblies to maintain reasonable rail/wheel loading. A present commonly used higher load freight car rail vehicle utilizes a four axle suspension, comprising one two-axle truck supporting each end of the rail vehicle. Each truck includes two axles, each generally held in a set of side frames with a bolster running between the side frames. The bolster of each truck is rotatably connected to a center plate associated with the connection to the freight car body. With such a 2-axle bolster rotatably mounted on opposite ends of the car, the car is able to self-steer around curves. For some higher load freight car applications it is known to use 3-axle trucks in place of the 2-axle trucks, with one 3-axle truck similarly mounted at each end of the rail vehicle, the truck bolster at each end of the rail vehicle being connected via a center plate. This arrangement provides a six axle (or twelve wheel) rail vehicle. The provision of two additional axles (four more wheels) can provide the desired higher carrying capacity of the rail vehicle. However, as the desire to carry increased loads has demanded additional axle sets (wheels), the dynamic performance of additional axles upon the car operation has been difficult to maintain consistent with existing track. One prior art solution to increasing the carrying capacity of rail vehicles has been to utilize twelve axles in four trucks, each truck having 3-axles. This type of rail vehicle employs a member known as a span bolster. A span bolster is rotatably connected to each end of the car body via a center plate. Then, the bolster of each of the two 3-axle trucks which support each end of the rail vehicle is rotatably mounted to the span bolster via a center plate. An example of one such vehicle is known as QTTX131100, and is manufactured by National Steel Car Limited, of Canada. While such a vehicle does have the weight capacity, resulting from the twelve axle/twenty-four wheel arrangement, the dynamics and performance of this rail vehicle on curved track can be less than desired.
Track curvature, and other roadway variables, can make multiple axle high speed rail operation difficult. In particular, the ability of the rail vehicle to safely traverse curved track sections can be degraded as the number of axle sets at each end of the rail vehicle is increased. The reason for this results from the circumstance that the center of each truck is held generally centered between the rails by the center plate connection and by virtue of the truck wheels being confined between the track rails. The center of each truck generally corresponds to the point of rotation of the center plate on the truck bolster. Although rotation is permitted, the center of each truck has generally been constrained in the lateral direction by the center plate connection. This is the case because the axles, via the wheels, of each truck are laterally constrained by the rails to a position generally centered between the rails. Yet, it is understood that there is some play, i.e., small degree of movement, inherent in all three piece trucks. As the trucks at the front and rear of the car body traverse curved track, the rails hold the center point of each truck to a position generally centered between the rails. On straight track, the center/center line of the car body will be generally aligned with the center line of the rails. However, the car body is rigid, i.e., does not xe2x80x9cbend,xe2x80x9d and thus cannot follow the curvature of the track. Consequently, the center of the rigid car body must laterally shift (toward the center of the radius of curvature) with respect to the rails when a curved track section is traversed. Generally, in order to enable lateral displacement of the center of the car body, each end of the car body must be free to rotate about the connection of the truck bolsters with respect to the other end of the car body. Where multiple trucks are employed at each end of the rail vehicle, a span bolster has been necessary to enable each end of the car body to rotate with respect to the trucks to provide the necessary lateral displacement when curved track is traversed.
However, a disadvantage the span bolster is that the deck height of the car body is increased due to the presence of the span bolster between the trucks and the car body. Additionally, the weight of the rail vehicle is increased by the weight of the span bolster and associated mounting members. Eliminating the span bolster would reduce the weight of the rail vehicle and enable a lower deck height, as well as simplifying and reducing the cost of making multiple truck, high weight capacity rail vehicles. Therefore, it would be desirable to provide a high load multiple axle rail vehicle which weighs less, has a low deck height, and maintains the necessary dynamic performance compatible with existing rail conditions.
According to the invention, a rail vehicle can be supported at each end by multiple trucks each connected individually to the car body of the rail vehicle. A center plate on each of the multiple trucks can be attached to separate, mating center plate mounts on the underside of the car body, at each end of the car body. Connecting each truck to an individual center plate mount on the car body eliminates the need for the span bolster which is conventionally connected intermediate the multiple trucks and the car body at each end of the rail vehicle. Elimination of the span bolster between the car body and the trucks permits the deck height of the rail vehicle to be significantly lower. Moreover, the weight of the rail vehicle can be reduced by the weight of the span bolster.
In a certain embodiment, a pair of trucks can be provided at each end of the rail vehicle. The trucks can be specially designed to provide an increased amount of lateral travel to accommodate lateral movement of the truck with respect to the car body sufficiently to permit the rail vehicle to travel curved track sections with the requisite dynamic performance compatible with existing track conditions. Additionally, the center plate connections between the trucks and the car body can be designed to provide a degree of lateral movement to supplement the lateral displacement enabled by the specially designed trucks. Each truck can be a specially modified swing motion type truck wherein the distance between transom stops is increased to permit more lateral travel for the bolster and a higher degree of lateral displacement of the bolster, and thus the center plate member. Additionally, non-standard spring sets can be utilized on one or more of the trucks, including taller springs, which further increase the amount of lateral displacement which can be provided. The increased height which can result from using taller springs can be offset by the lower height enabled by elimination of the span bolster.
Other details, objects, and advantages of the invention will become apparent from the following detailed description and the accompanying drawings FIGS. of certain embodiments thereof.